U.S. patent number 6,322,470 [Application Number 09/572,739] was granted by the patent office on 2001-11-27 for pivoting dual arm chain tensioner system for contacting multiple chain strands.
This patent grant is currently assigned to BorgWarner Inc.. Invention is credited to George L. Markley, Mark M. Wigsten.
United States Patent |
6,322,470 |
Markley , et al. |
November 27, 2001 |
Pivoting dual arm chain tensioner system for contacting multiple
chain strands
Abstract
An engine tensioning system including a pair of pivoting arms
used to simultaneously tension two separate strands of the same
chain in an engine timing system. The tensioner system includes a
lever. The lever has a pair of fixed pins attached to an end
located between the two strands of chain. The arms extend outside
separate strands of the chain and carry shoes positioned to contact
an outside portion of the chain are pivotally mounted to the fixed
pins. Rotation of the lever causes the fixed pins to move laterally
with respect to the chain strands and cause the arms to draw
inwardly. The inward movement of the arms draw the shoes into
contact with the chain strands and impart tension to the separate
strands of the chain simultaneously.
Inventors: |
Markley; George L. (Montour
Falls, NY), Wigsten; Mark M. (Lansing, NY) |
Assignee: |
BorgWarner Inc. (Troy,
MI)
|
Family
ID: |
24289146 |
Appl.
No.: |
09/572,739 |
Filed: |
May 17, 2000 |
Current U.S.
Class: |
474/111;
474/122 |
Current CPC
Class: |
F16H
7/08 (20130101); F16H 2007/0812 (20130101); F16H
2007/0859 (20130101); F16H 2007/0874 (20130101) |
Current International
Class: |
F16H
7/08 (20060101); F16H 007/08 () |
Field of
Search: |
;474/110,111,112,119,122,128,129,101 ;123/90.15 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Green; Mary Ann
Attorney, Agent or Firm: Sidley Austin Brown & Wood
Dziegielewski; Greg
Claims
What is claimed is:
1. A pivoting dual arm chain tensioner system for a power
transmission chain wrapped around a plurality of rotating
sprockets, said chain having a pair of strands extending between
the sprockets, said tensioner system comprising:
a lever, said lever having a first end with a central pivot bore,
said pivot bore being located between said pair of strands of said
chain, said lever having a second end opposite said first end, said
second end having a contact surface;
a first fixed pin and a second fixed pin, said first and second
fixed pins being fixedly attached to said first end and spaced
apart from each other;
a first arm disposed on said first fixed pin to permit rotation of
said first arm with said first fixed pin about said central pivot
bore, said first arm extending outside a first strand of said
chain, said first strand being a slack strand, said first arm
having a first shoe attached thereto for contacting said slack
strand;
a second arm disposed on said second fixed pin to permit rotation
of said second arm with said second fixed pin about said central
pivot bore, said second arm extending outside a second strand of
said chain, said second strand being a tight strand, said second
arm having a second shoe attached thereto for contacting said tight
strand;
an actuator positioned to contact said contact surface of said
second end of said lever, said actuator acting upon said contact
surface of said lever to cause said lever and said first and second
fixed pins to rotate about said central pivot bore and to thereby
cause movement of said first and second arms and said first and
second shoes to impart tension to said chain strands.
2. The pivoting dual arm chain tensioner system of claim 1 wherein
said first and second fixed pins are positioned on said first end
of said lever to thereby cause movement of said first and second
arms in a direction perpendicular with respect to a centerline
drawn between said sprockets and through said central pivot bore to
impart tension to said chain strands.
3. The pivoting dual arm chain tensioner system of claim 1 wherein
said lever includes a first central axis extending from said first
end to said second end and through said central pivot bore and
dividing said lever into upper and lower portions, said first fixed
pin is located below said central axis and said second fixed pin is
located above said central axis.
4. The pivoting dual arm chain tensioner system of claim 3 wherein
said first and second fixed pins are in substantial alignment with
said pivot bore along a second axis that is generally perpendicular
to said first central axis, said first and second fixed pins being
equally spaced apart from said pivot bore along said second
axis.
5. The pivoting dual arm chain tensioner system of claim 3 wherein
said first fixed pin is spaced a first distance from said central
axis and said second fixed pin is spaced a second distance from
said central axis, said first distance being different from said
second distance.
6. The pivoting dual arm chain tensioner system of claim 3 wherein
said first arm is provided with a first tensioning force and said
second arm is provided with a second tensioning force, said first
force being greater than said second force.
7. The pivoting dual arm chain tensioner system of claim 1 wherein
said first and said second arms are each pivoted about a single
point, said pivoting movement of said arms permitting said arms to
adjust to movement of said chain strands along said arms.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to tensioners used with
chain drives in automotive timing and power transmission
applications. In particular, the present invention is related to a
chain tensioner system having a pair of arms. The arms are
positioned outside opposite strands of chain in a power
transmission system. The tensioner system causes the arms to travel
inwardly towards a chain centerline which acts to simultaneously
tension the two strands of a chain in an engine timing
application.
Chain tensioning devices, such as hydraulic tensioners, are used as
control devices for power transmission chains as the chain travels
between a plurality of sprockets. In an automotive application, the
tension of the chain can vary greatly due to the wide variation in
the temperature and the linear expansion among the various parts of
the engine. Moreover, wear to the chain components during prolonged
use can produce a decrease in the tension of the chain. As a
result, it is important to impart and maintain a certain degree of
tension to the chain to prevent noise, slippage, or unmeshing of
the chain with the sprocket teeth. It is especially important in
the case of a chain-driven camshaft in an internal combustion
engine to prevent the chain from slipping because the camshaft
timing can be misaligned by several degrees, possibly rendering the
engine inoperative or causing damage.
A hydraulic tensioner as used with a tensioner arm or shoe is shown
in Simpson et al., U.S. Pat. No. 5,967,921, which is incorporated
herein by reference. Hydraulic chain tensioners typically have a
plunger slidably fitted into a chamber and biased outward by a
spring to provide tension to the chain. A lever, arm or shoe is
often used at the end of the plunger to assist in the tensioning of
the chain. The hydraulic pressure from an external source, such as
an oil pump or the like, flows into the chamber through passages
formed in the housing. The plunger is moved outward against the arm
by the combined efforts of the hydraulic pressure and the spring
force.
When the plunger tends to move in a reverse direction (inward) into
the housing, typically a check valve is provided to restrict the
flow of fluid from the chamber. In such a fashion, the tensioner
achieves a so-called no-return function, i.e., movements of the
plunger are easy in one direction (outward) but difficult in the
reverse direction. In addition, rack and ratchet mechanisms, which
are well known in the art are employed to provide a mechanical
no-return function.
One example of a chain tensioner which uses a hydraulic tensioner
and a pivoted lever to tension a chain is described in Sato et al.,
U.S. Pat. No. 5,318,482. Sato et al. show a conventional hydraulic
tensioner with a plunger pressing a pivoted lever against a chain
to impart an appropriate tension to the chain. The tensioner and
single shoe arm of Sato et al. has limitations, however, in the
amount of chain slack it can take up during the life of the chain.
In addition, the single shoe arm of Sato et al. has limitations in
its ability to absorb and damp cyclic vibrations in the chain
during operation.
Conventional prior art tensioners which tension only one strand of
chain, i.e., a single length of chain between two sprockets, in an
engine timing application with long center distances between the
sprockets have a common weakness. During operation of the engine,
wear on the various chain parts causes the chain to lengthen.
Taking up the resulting slack on one side of an engine timing
system and not the other can cause the timing of the camshaft to
change relative to the crankshaft. In some engine timing chain
applications, the large center distances cause both sides of the
chain span between sprockets to slacken as the chain wears and
extends in length.
To address the above problems the present invention includes an
actuator, in the form of a conventional hydraulic tensioner in
combination with a pivoting lever. The lever has a pair of fixed
pins on opposite sides of a central pivot bore. The fixed pins each
carry an arm with each arm carrying an attached shoe. In
combination, the shoes contact and act on separate strands of a
common chain. This provides potentially double the operating
take-up for a given range of tensioner operation as compared to a
conventional hydraulic tensioner acting upon a single arm with an
end pivot that acts on one chain strand.
When the present invention is used to tension separate strands of a
single chain, vibrations which occur in one strand of chain tend to
be cancelled when the energy of those vibrations are transferred to
or combined with those in another strand through the pivoting
tensioner. Further, when taking up chain slack in an engine timing
application, the present invention minimizes the chance for changes
in the timing between the crankshaft and the camshaft as the chain
wears and slackens on both sides of the chain span between the
sprockets.
SUMMARY OF THE INVENTION
The present invention provides a chain tensioner system which
includes an actuator which may be a conventional hydraulic
tensioner, in conjunction with a pivoting lever. The lever carries
a pair of pivoting arms. The arms extend outside of and contact
both lengths or strands of the span of chain between a pair of
sprockets. Actuation of the tensioner against the lever causes
rotation of the lever which causes inward motion of the arms. The
inward motion of the arms causes tension to be imparted to both
strands of the chain simultaneously.
One example of the chain tensioner system of the present invention
includes a hydraulic actuator as described above and a pivoting
lever. Alternately, the actuator may be a mechanical tensioner or
any suitable mechanism which is capable of providing sufficient
force and travel to act on the lever to provide an adjustment in
tension of the chain. The chain has two opposite strands, spans or
lengths that are the portions extending between the sprockets. The
strand between the sprockets where the chain leaves a driven
sprocket and enters a driving sprocket is typically the tight
strand or side and the strand between the sprockets where the chain
leaves the driving sprocket and enters the driven sprocket is
typically the slack strand or side of the chain. However, in
systems with large center distances, both sides of the chain
evidence some slack.
The lever includes a first end which is located between the chain
strands. In the center of the first end of the lever is a pivot
bore. The pivot bore is a hole with a cylindrical sleeve or bushing
through which a pivot pin, shaft or bolt is inserted and about
which the lever may rotate. The pivot pin is attached to an engine
block or a mounting surface. The pivot bore and pivot pin are
centered on a centerline extending between the two sprockets.
A pair of fixed pins are attached near the periphery of the first
end of the lever. The fixed pins are located in near alignment with
the chain centerline and equally spaced apart on opposite sides of
the pivot bore. A pair of arms, each with an attached plastic shoe,
are mounted to and allowed to rotate on each of the fixed pins. The
arms extend outside the strands of the chain such that the shoes
are positioned to contact an outside portion of the chain. A first
arm and associated shoe extend outside the slack strand and a
second arm and shoe extend outside the tight strand of chain.
A first fixed pin which is mounted to the lever in a position
generally below the pivot bore carries the first arm. The first arm
extends outside the slack strand of the chain (assuming a pair of
sprockets with a wrapped chain traveling in a clockwise direction).
A second fixed pin which is mounted to the lever in a position
generally above the pivot bore carries the second arm. The second
arm extends outside of the tight strand of the chain.
A second end of the lever extends a distance from the first end of
the lever and extends outside the loop of the chain. The second end
of the lever has at least one contact surface. It should be
understood that the second end of the lever may be located in a
number of equivalent positions.
In operation, actuation of the tensioner directs a force to the
second end of the lever which causes rotation of the lever about
the pivot pin. The fixed pins mounted on the first end of the lever
pull the mounted arms in toward the chain centerline. For example,
when the lever rotates in a counterclockwise direction, the first
fixed pin and first arm are moved in a direction toward the chain
centerline. Since the first arm is located outside the slack strand
of the chain the inward travel of the first arm imparts an
increased tension to the slack strand by displacing the slack chain
strand path toward the chain centerline. Simultaneously, the second
fixed pin and second arm are moved in a direction toward the chain
centerline. Since the second arm is located outside the tight
strand of the chain, the inward travel of the second arm imparts an
increased tension to the tight strand by displacing the tight chain
strand path toward the chain centerline.
Pivoting the lever about the pivot bore by applying a force to the
contact surface causes the fixed pins to draw the arms and shoes
inwardly into contact with the chain strands thereby causing the
chain to be squeezed inwardly toward the centerline and tensioned
on both tight and slack strands simultaneously.
In a second embodiment of the present invention, the pins mounted
upon the lever are located different distances from the center of
the pivot bore. In this manner, the fixed pin which is located
closer to the center of the bore (the center of rotation) produces
less take-up motion in the attached arm. This feature would be
useful in the situation where less take-up is desired in the tight
strand compared to the slack strand of a chain.
For a further understanding of the present invention and the
objects thereof, attention is directed to the drawing and the
following brief description thereof, to the detailed description of
the preferred embodiment of the invention and to the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front view of the present invention.
FIG. 2 is a front view of the lever of the present invention.
FIG. 3 is a bottom view of the lever of FIG. 2.
FIG. 4 is a front view of the arm of the present invention.
FIG. 5 is a side view of the arm of FIG. 4.
FIG. 6 is a front view of the shoe of the present invention.
FIG. 7 is a side view of the shoe of FIG. 6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to the drawings, FIG. 1 shows a front view of a
preferred embodiment of the present invention. In this figure, an
engine timing system is represented generally by crankshaft
sprocket 10 (the drive sprocket) and camshaft sprocket 12 (the
driven sprocket). The path of a power transmission chain, i.e., a
silent chain, roller chain or the like, is represented by broken
chain line 14 wrapped around the drive sprocket 10 and the driven
sprocket 12. The path of a power transmission chain which has
elongated due to wear is represented by broken chain line 15. The
tensioner system of the present invention is located between the
tight and loose strands of the chain and between the two
sprockets.
The tensioner system includes an actuator 16 which may be a
hydraulic tensioner or the like. In the present illustration, the
actuator 16 is represented by housing 18 and plunger 20. The
plunger is biased in an outward direction from the housing by
spring 17. The housing 18 is mounted to a fixed mount or engine
block (not shown). The plunger extends outwardly from the
housing.
The tensioner system includes a pivoting lever 30 which carries a
pair of arms 60, 61 with attached shoes 70, 71. The lever 30 has a
first end 31 with a generally circular shape positioned between the
opposite strands of the chain 14 and centered with respect to a
centerline C extending between the center of the drive 10 and the
driven sprocket 12. The center of the first end 31 of the lever 30
has a pivot bore 32 formed therein. The pivot bore 32 is provided
with a bushing 33. The pivot bore 32 and bushing 33 are centered
with respect to the centerline C. The first end 31 receives a fixed
pivot pin 25 in the pivot bore 32 which allows the lever 30 to
pivot about the pivot pin 25. The pivot pin 25 may be fixed to a
mounting surface or an engine block (not shown).
A second end 34 of the lever 30 extends to the outside of the chain
14. The second end 34 has a contact surface 35 extending generally
perpendicular to the lever 30. The plunger 20 of the actuator 16 is
positioned to act against the contact surface 35. A combination of
spring and fluid pressure causes the plunger 20 to extend from the
housing 18 and causes the lever 30 to rotate about the pivot pin
25, as shown in this illustration, in a counterclockwise direction
D.
A pair of fixed pins 36, 37 are attached to the lever 30 near the
periphery of the circular first end 31 on opposite sides with
respect to the pivot bore 32. A first fixed pin 36 is located below
the pivot bore 32 and slightly to the left of the centerline C near
the slack chain strand. A second fixed pin 37 is located above the
pivot bore 32 and slightly to the right of the centerline C. The
first and second pins are located equidistant from the center of
the pivot bore. In this arrangement, movement of the lever 30 about
the pivot pin 25 causes the fixed pins 36, 37 to move equally in a
lateral direction, indicated in the direction M, substantially
perpendicular with respect to the centerline C.
A first arm 60 is rotatably attached to the first fixed pin 36. The
first arm 60 extends outside the slack strand 14A of the chain 14
and carries a shoe 70 with a wear face 72 positioned to contact the
outside portion of the chain strand 14A. A second arm 61 is
rotatably attached to the second fixed pin 37. The second arm 61
extends outside the tight strand 14B of the chain 14 and carries a
shoe 71 with a wear face 73 positioned to contact the outside
portion of the chain strand 14B.
In operation, the plunger 20 moves the second end 34 of the lever
30 (in direction D) about the pivot pin 25 causing a
counterclockwise movement of the first end 31 of the lever 30. In
this manner, the fixed pins 36, 37 pull the arms 60, 61 and
attached shoes 70, 71 laterally toward the chain centerline C and
into contact with outside portions of the chain strands 14A, 14B.
As the arms are pulled by the fixed pins into a position closer to
the chain centerline C, the chain is essentially squeezed or
tightened from both sides or along both spans, simultaneously and
tension is imparted to the chain strands accordingly.
In this manner, the tensioner system of the present invention will
potentially produce approximately double the take-up for a given
range of tensioner operation as compared to a conventional
hydraulic tensioner acting upon a single arm with an end pivot that
acts on one chain strand. Additionally, vibration in a first strand
of chain, whether it be the loose or tight strand is transferred
and damped by action of the second strand of chain due to the
coupling of the two arms through the lever.
FIG. 2 depicts the lever 30 of FIG. 1 in a front view. The first
end 31 has a generally circular shape with a pivot bore 32 in the
center. It should be understood that the first end of the lever may
be a number of shapes. The pivot bore 32 has a bushing 33 disposed
therein. Spaced equally apart and on opposite sides of the pivot
bore near the periphery of the circular first end 31 are a first
fixed pin 36 and a second fixed pin 37. The lever 30 has a second
end 34 with first contact surface 35A and second contact surface
35B, formed perpendicular to the lever, which enable the lever to
be assembled into the tensioner system in a right facing or left
facing orientation. In other words, the lever 30 may be used in a
tensioner system with the second end 34 extending outside of either
side of the chain and sprocket system. Alternately, the lever may
be oriented along the chain centerline in a chain and sprocket
system where the center-to-center distance between sprockets
provides sufficient space for the lever.
FIG. 3 depicts a bottom view of the lever of FIG. 2. In particular,
the contact surface 35B is a rectangular tab oriented perpendicular
to the main body portion of the lever 30 at the second end 34 of
the lever. The first fixed pin 36 is shown in alignment with the
pivot bore 32 near the first end 31 of the lever 30.
FIG. 4 depicts an arm 60 in a front view. The first and second arms
(60, 61 as shown in FIG. 1) are identical in structure but oriented
to operate on a strand of chain depending on the direction of chain
travel. The arm 60 has an elongated bracket portion 60A with a bore
80. The bore 80 is slightly offset toward the leading end of the
bracket portion 60A of the arm 60. More particularly, the bore 80
is offset toward the end of the arm 60 nearest the incoming
chain.
The arm has a shoe attachment portion 60B, also shown in FIG. 5,
which is oriented perpendicular to the elongated bracket portion
60A. The face attachment portion 60B has a lengthwise gradual curve
to generally match an associated span of chain and a plurality of
rectangular openings 82A, 82B, 82C to facilitate the attachment of
a plastic shoe.
The shoe portion 70 of the tensioner system is shown in FIGS. 6 and
7. The shoe includes a plurality of clips 74A, 74B, 74C formed on a
back side of the shoe which insert through the rectangular openings
in the shoe attachment portion of the arms. In particular, clip 74A
engages hole 82A shown in FIG. 5. Similarly, clip 74B engages hole
82B and clip 74C engages hole 82C.
Preferably, a clip is formed at each end of the shoe and another
clip is formed in an intermediate portion of the shoe. Opposite the
back side is a chain contacting wear face 72A, preferably with a
flat central face and raised edges 72B, 72C to form a channel over
which the chain travels.
While several embodiments of the invention are illustrated, it will
be understood that the invention is not limited to these
embodiments. Those skilled in the art to which the invention
pertains may make modifications and other embodiments employing the
principles of this invention, particularly upon considering the
foregoing teachings.
* * * * *